Impact of agro-chemicals on the management of foliar diseases in cotton

Cotton is the most important fiber crop of India having largest area (11.0 m ha) but the present lint productivity of 503 kg hectare^–1 is very low in comparison to other countries. In Punjab cotton is being cultivated in about 0.55 m hectares with a production of 16–17 lakh bales and productivity of 528 kg/ha. Among various productivity constraints, foliar diseases caused by fungal and bacterial pathogens aminly bacterial blight (Xanthomonas axonopodis pv. Malvacearum) and leaf spots (Alternaria macrospora, Myrothecium rordium and Cercospora gossypina) are of major concern. In the present study, different doses of Kresoxim methyl (Ergon) along with Blitox + Streptocycline sulphate has been evaluated in under natural epiphytotic conditions during kharif 2010–11 at PAU, Regional Station, Faridkot. Bt hybrid MRC 6304 was sown during 4^th. week of April at a spacing of 75.0 X 67.5 cm with plot size of 27.3 m². Recommended package of practices were followed to raise the crop. Five doses of Kresoxim methyl (Ergon) @ 300, 400, 500 ml/ha; Carbendazim @ 0.1% and a combination of Blitox + Streptocycline sulphate ((3g + 0.5 g/l) were sprayed thrice at an interval of 15 days starting from the initial appearance of the disease. Observations on the disease severity were made 10 days after last spray of fungicides using 0–4 disease scoring scale. The observations on field efficacy of chemicals showed that out of six treatments, Kresoxim methyl (Ergon) @ 400 ml/ha managed 59.2% foliar leaf spots and exhibited highest seed cotton yield (23.4 q/ha) as compared to other treatments. Though the standard check (Blitox + Streptocycline sulphate) caused only 55.1% disease reduction with non-significant difference in yield. Kresoxim methyl (Ergon) @ 500, 1000 and 2000 ml/ha did not cause phytotoxicity even upto 15^th days of spraying. Therefore these chemicals could retain inputs for longer time and give disease control over extended period of time.